The National Weather Service has issued a flash flood watch for all islands, effective through late tonight.

According to the weather service, a very moist air mass spreading northeast toward the main Hawaiian islands will bring widespread cloud cover and rain.

Steady rain was expected to begin on Kauai last night and spread to the other islands overnight and today. Upslope showers may also develop early along south-facing slopes of the big island.

A high-surf advisory is also in effect for north- and east-facing shores of Niihau, Kauai, Oahu, Molokai, Maui and the Big Island through Tuesday.

Surf along north-facing shores is expected to rise to 12 to 15 feet. Surf along east-facing shores exposed to the north swell is expected to reach 8 to 12 feet.